The three states of matter

This question is about alloys. Solders are alloys of tin and lead. Different solders have different percentages of tin and lead. Figure 4 shows the arrangement of atoms in pure tin and in a solder.

The solder in Figure 4 has 6 lead atoms for every 24 tin atoms. Determine the percentage of atoms that are lead atoms in the solder in Figure 4.

Explain why solder is harder than pure tin. Complete the sentences. Use Figure 4. In solder the layers are distorted.

Therefore the layers cannot easily

Figure 5 shows how the melting point of the solder changes with the percentage by mass of tin in the solder.

Describe what happens to the melting point of the solder as the percentage by mass of tin increases. Use data from Figure 5.

What is the melting point of pure tin? Use Figure 5.

What happens to the atoms in pure tin as the tin melts? Tick (✓) one box.

This question is about electrolysis.

Ionic compounds decompose when they are electrolysed.

A student electrolyses sodium sulfate solution.

Figure 13 shows the apparatus used.

Sodium sulfate solution contains:

• hydrogen ions

• hydroxide ions

• sodium ions

• sulfate ions.

Oxygen is produced at the positive electrode.

Which ions are discharged at the positive electrode to produce oxygen?

Tick (✓) one box.

Figure 14 shows one of the measuring cylinders during the electrolysis.

What is the volume of gas in the measuring cylinder?

Ionic compounds can be electrolysed when molten or dissolved in water.

Why can ionic compounds not be electrolysed when solid?

You should answer in terms of ions.

Table 7 shows the products of electrolysis of two molten compounds.

Complete Table 7.

The electrolysis of molten sodium chloride is used to extract sodium metal.

Why is sodium metal extracted by electrolysis instead of by reduction with carbon?

Tick (✓) one box.

What is the state symbol for molten sodium chloride?

Tick (✓) one box.

Titanium can be produced from titanium oxide by electrolysis.

The equation for the reaction is:

Calculate the percentage atom economy for the production of titanium from titanium oxide by electrolysis.

Use the equation:

Relative atomic mass (A_r): Ti = 48

Relative formula mass (M_r): TiO₂ = 80

This question is about the reaction between hydrogen sulfide (H₂S) and oxygen. The equation for the reaction is:

What does H₂O(g) represent?

Calculate the volume of oxygen required to react with 50 cm³ of hydrogen sulfide.

Figure 6 shows part of the reaction profile for the reaction. The reaction is exothermic. Complete Figure 6. You should:

• complete the profile line

• label the activation energy

• label the overall energy change.

Figure 7 shows the displayed formula equation for the reaction of hydrogen sulfide with oxygen.

Figure 7

Table 5 shows some of the bond energies.

In the reaction the energy released forming new bonds is 1034 kJ/mol greater than the energy needed to break existing bonds. Calculate the bond energy X for the bond. Use Figure 7 and Table 5.

This question is about structure and bonding.

Which two substances have intermolecular forces between particles? Tick (✓) two boxes.

Table 1 shows the structures of three compounds.

Compare the structure and bonding of the three compounds:

• carbon dioxide

• magnesium oxide

• silicon dioxide.

This question is about displacement reactions.

The displacement reaction between aluminium and iron oxide has a high activation energy. What is meant by ‘activation energy’?

A mixture contains 1.00 kg of aluminium and 3.00 kg of iron oxide. The equation for the reaction is:

Show that aluminium is the limiting reactant. Relative atomic masses (A_r): O = 16 Al = 27 Fe = 56

Magnesium displaces zinc from zinc sulfate solution.

Complete the ionic equation for the reaction. You should include state symbols.

Explain why the reaction between magnesium atoms and zinc ions is both oxidation and reduction.

The reaction between hydrogen and oxygen releases energy.

A student drew a reaction profile for the reaction between hydrogen and oxygen. Figure 3 shows the student’s reaction profile.

The student made two errors when drawing the reaction profile. Describe the two errors.

The reaction between hydrogen and oxygen in a hydrogen fuel cell is used to produce electricity. Hydrogen fuel cells and rechargeable cells are used to power some cars. Give two advantages of using hydrogen fuel cells instead of using rechargeable cells to power cars.

Reactions occur at the positive electrode and at the negative electrode in a hydrogen fuel cell. Write a half equation for one of these reactions.

The three states of matter can be represented by a simple particle model. Figure 4 shows a simple particle model for hydrogen gas.

Give two limitations of this simple particle model for hydrogen gas.

The hydrogen gas needed to power a car for 400 km would occupy a large volume. Suggest one way that this volume can be reduced.

The energy needed for a car powered by a hydrogen fuel cell to travel 100 km is 58 megajoules (MJ). The energy released when 1 mole of hydrogen gas reacts with oxygen is 290 kJ The volume of 1 mole of a gas at room temperature and pressure is 24 dm³ Calculate the volume of hydrogen gas at room temperature and pressure needed for the car to travel 100 km

A student investigated the reaction between lumps of calcium carbonate and dilute hydrochloric acid. This is the method used.

1. Pour 100 cm³ of dilute hydrochloric acid into a conical flask.

2. Place the conical flask on a balance.

3. Add 2 g of calcium carbonate lumps to the conical flask.

4. Wait until the calcium carbonate stops reacting.

5. Record the decrease in mass of the conical flask and contents.

6. Repeat steps 1 to 5 three more times.

The equation for the reaction is:

What is the state symbol X in the equation? Tick (✓) one box.

Table 2 shows the student’s results.

Why does the mass of the conical flask and contents decrease during the reaction? Tick (✓) one box.

What is the range of the four results in Table 2 ?

Calculate the mean decrease in mass of the conical flask and contents. Do not include the anomalous result. Use Table 2.

A teacher demonstrated the investigation. The teacher used different masses of calcium carbonate. Figure 8 shows the teacher’s results.

What type of variable is the mass of calcium carbonate? Tick (✓) one box.

Use Figure 8 to answer Questions 05.6 and 05.7

Complete the sentence. As the mass of calcium carbonate used increases, the decrease in mass of

What is the decrease in mass of the conical flask and contents when a 3 g sample of calcium carbonate is used?

A student investigated the mass of copper oxide produced by heating copper carbonate.

This is the method used.

1. Weigh an empty test tube.

2. Weigh 2.00 g of copper carbonate into the test tube.

3. Heat the copper carbonate until there appears to be no further change.

4. Re-weigh the test tube and copper oxide produced.

5. Subtract the mass of the empty tube to find the mass of copper oxide.

6. Repeat steps 1–5 twice.

7. Repeat steps 1–6 with different masses of copper carbonate.

Table 4 shows the student’s results.

The equation for the reaction is:

Complete the sentence.

Why do the contents of the test tube lose mass in the investigation?

Calculate the mean mass X in Table 4.

One of the results in Table 4 is anomalous.

Which result is anomalous?

Determine the mass of magnesium oxide produced by 8.4 g of magnesium carbonate.

Use Figure 8.

Calculate the mass of magnesium oxide produced when 168 g of magnesium carbonate is heated.

Use your answer to Question 05.7